WO2008083861A1

WO2008083861A1 - Transparent organic-based electrochromic formulation, production of a transparent electrochromic component, and uses therefor

Info

Publication number: WO2008083861A1
Application number: PCT/EP2007/059586
Authority: WO
Inventors: Andreas Kanitz; Wolfgang Roth; Roland Wagner; Julia Wirsing
Original assignee: Siemens Aktiengesellschaft
Priority date: 2007-01-11
Filing date: 2007-09-12
Publication date: 2008-07-17

Abstract

The invention relates to an electrochromic formulation which is transparent in the visible spectral range. The transparency of the formulation comes about as a result of light scattering, which is induced by particles in the formulation. The transparency can be adjusted via the particle size and the layer thickness.

Description

description

Transparent organic based electrochromic formulation, preparation of a transparent electrochromic device and uses therefor

The invention relates to an electrochromic formulation which is transparent in the visible spectral range.

Electrochromic devices that are transparent in the visible spectral range are suitable for specific applications such as windows and mirrors. E lektrochrome transparent components previously known only inorganic based, ^¬ are too expensive very aufwen dig in the manufacture and therefore nen for large Applikatio-.

Electrochromic displays based on organic materials to take ^¬ normally an active electrochromic layer, which is in the case of a display between the electrodes arranged perpendicular to each other. Essential components of the active layer are a redox system and a pH-active dye. By applying a voltage, the concent ^¬ rationsverhältnis the redox partner is shifted from each other in the material. In this reaction protons and / or ions are released or bound in the material, which has an effect on the pH. When a voltage is applied to the material at ^¬, then the displacement of the equilibrium of the redox partners of the two electrodes run in the opposite direction. This causes the pH at one electrode to rise while it sinks at the counterelectrode. Via a pH dye, the change in the pH value is then converted into a color change of the material and the application of the voltage is made visible.

It is known from WO 02 / 075441A2 and WO 02/075442 A1 that a pasty formulation, which represents the electrochromic system, is located between the electrodes. The composition of this electrochromic system comprises as essential constituents a polymer as a solid electrolyte, a conductive salt, a redox system, TiO ₂ as a white pigment, a solvent and ei ^¬ nen dye. This is usually a pH indicator. Although alternatives to TiO ₂ as a white pigment are known, however, these find practically no application because of their low hiding power.

Another principle to realize electrochromic displays is to bring about the color change not by changing the pH in the display, but to use the already occurring redox processes to produce high-contrast color changes by the formation of reductive and / or oxidative states in suitable materials , In particular, the so-called viologens and polythiophenes have become known as classes of materials. Examples in the literature for this are described in M.O.M. Edwards, Appl. Phys. Lett. 2005, 86 (7) and Helmut W. Heuer, Rolf Wehrmann, Stephan Kirchmeyer Adv. Funct. Mater. 2002, 89.

Since a unterschiedli ^¬ cher color impression usually arises at the cathode or anode, a white pigment must be used to suppress the color impression of the, the viewer off, electrode. TiO _{2 is} widely used as a white pigment with high ^{covering power} . Cause a reduction of the content of white pigment, the layer thickness and / or the content of the electrochromically Akti ^¬ ven component to only unsatisfactory results to produce a transparent, that is translucent impression with backlighting.

Object of the present invention is therefore to provide an orgasmic ^¬ based electrochromic active formulation, with which a transparent electrochromic organic component can be produced.

This object is achieved by the subject matter of the claims, the description and the examples. The invention relates to an electrochromic formulation comprising the following materials: at least one chromophore and at least one associated redox partner in a matrix, inorganic and / or organic particles which are dispersed in the formulation and thus produce light scattering in the matrix. Moreover, the invention relates to a method for producing a transparent electrochromic organic component and finally the invention relates to the use of transparent electrochromic components in state displays, windows and / or mirrors.

Suitable inorganic particles that cause the light ^¬ scattering in the matrix, are suitable, for example calcium carbonate, barium sulfate, talc, generally carbonates, bicarbonates, sulfates, hydrogen sulfates and phosphates, hydrogen phosphates of alkali and alkaline earth elements. Particularly suitable is calcium carbonate. Furthermore, oxides, hydroxides and / or mixtures thereof of the metals of the third and fourth main group can be used. As organic solvents or dispersing z. As polyethylene glycols particularly suitable. A particularly suitable system consists of silicon dioxide, preferably with particle sizes of 4 to 20 μm, dispersed in diethylene glycol.

The light scattering that occurs in the formulation can also be detected by the Tyndall effect. This means that the formulation is colloidal systems whose particle sizes are in the wavelength range of visible light. Depending on the particle size, the formulation may show high transparency in the visible spectral range or be opaque and opaque.

To produce a transparent organic electronic component, the formulation is arranged between two switchable electrode layers.

When using such a component in status indicators, they can also be backlit. In the following is described a way to quantify the Transparent ^¬ ence of an electrochromic cell by an appropriate measurement.

FIG. 1 shows the measurement setup for the so-called CVC measurement (current-voltage-contrast), in which a cyclic voltammetry of the overall electrochromic system is carried out and at the same time the discoloration and the transient current are recorded.

In the CVC measurement, the transparent electrochromic cell 1 is irradiated with a light source 2, while the measured re ^¬ inflected light 3 with a photodetector. 4 In this case, the transparent EC display 1 is switched (circuit not shown for the sake of simplicity) that the Pho ^¬ todetektor 4 facing away from 5 darkened. The light source 2 irradiates the transparent ^¬ EC cell 1 with festgeleg ^¬ ter intensity (white LED 30OmCd). If the EC cell 1 is not transparent, the color of the side 6 facing the photodetector does not change and the same intensity is reflected as in the non-connected state and the current of the photodetector 4 remains high.

However, if, as is possible with embodiments of the formulation according to the invention, the discoloration of the opposite side 5 can be seen through the EC cell, ie if the EC cell is transparent, then the photodetector current necessarily sinks because the intensity of the reflected light decreases Absorption of part of the incident light in the discolored material).

The contrast is obtained by a darkening of the irradiated (and measured) surface in which the distance from the highest (initial state) at the lowest (Wired Mechanical state) Pho ^¬ todetektorstrom is determined. The measurement is carried out for both sides (5,6), so it is once the photo ^¬ detector 4 facing side 6 and once the opposite side 5 examined. The ratio of the measured contrasts for both cases provides as a first approximation a measurable statement for the transparency of the EC device. In the figures examples of different transparent EC displays are presented.

Figure 2: not transparent

Facing side 6: discoloration (I max - I min = 0.7) Facing side 5: no discoloration (I max - I min <0.1)

Figure 3: slightly transparent

Facing side 6: discoloration (I max - I min = 0.5)

Page 5: slight discoloration (I max - I min = 0.25)

Figure 4: transparent

Facing side 6: discoloration (I max - I min = 0.7) Facing side 5: discoloration (I max - I min = 0.7)

The same transparent electrochromic cells were still subjected to a UV / VIS measurement. The results can be seen in FIGS. 5 to 7.

According to a further advantageous embodiment, the formulation comprises a matrix in which a material for electrorochromic layers is based on a color change activated by redox reaction. In this case (see DE 10 2005 031 636.) Can ^¬ example, the functionality of the redox system, the electroactive tive chromophore and the polymer electrolyte in a component folded in.

By combining the functionalities, individual components of the electrochromic formulation are saved and the lifetime of the electrochromic formulation is increased.

However, the formulation can be described 10 2005 031634 and DE 10 2005 032081, also comprise a material such example ^¬ example in the documents DE. Another embodiment of the invention is a matrix based on organic particles and consists in principle of a polymer in an only moderately good solvent. The transparent impression results from only incompletely dissolved polymer particles. Particularly suitable is a mixture of polyvinylpyrrolidone, preferably with MW 1,300,000, or polyvinylcarbazole, preferably with MW 1,100,000 or polyethylene glycol, preferably with MW> 600,000 in diethylene glycol.

Surprisingly niedermole ^¬ molecular-weight organic compounds with a suitable organic solvent matrices according to the invention are obtained with appropriate opacity by combination. Such matrices are advantageous by dissolving the low molecular weight component in the solvent in the boiling heat, for. B. also by formation of a polymer, Herge ^¬ provides. During slow cooling, the low molecular weight compound or the polymer formed precipitates out as a finely divided phase and remains dispersed at suitable concentration ratios in the liquid phase. Particularly suitable is the combination of pyromellitic anhydride and diethylene glycol ^¬ (polymer formation).

In the matrix with the particles, an electrochromic active component, for example a polymeric 4,4'-bipyridinium salt (10 2005 032 316.2 DE, poly (dodecyl-4, 4 '- bipyridinium) -dibromid), mixed.

Particularly important for obtaining long-term stable transparent electrochromic cells, according to a preferred embodiment, the materials are used anhydrous.

Especially preferred is the use of anhydrous and / or free of water of crystallization materials, because protic electrochemical reactions which disturb the redox chemistry of the EC cell and in particular attack the electrode materials are avoided. By the content of the coloring component, the color depth can be adjusted by the content of the dispersed / colloidal particles, the transparency. According to further advantageous embodiments, the color depth or the transparency can be adjusted by the layer thickness. The electrochromic formulation with a layer thickness of less than 500 microns, more preferably less than 50 microns, transparent as a thin layer, in particular ^¬ sondere.

embodiments

1 Preparation of an opaque matrix with SiO ₂

6g SiO ₂ at 4-20 μm are mixed with 0.6 g of a polymeric bipyridium salt (poly (dodecyl-4,4'-bipyridinium) -dibromide) and 0.23 g of a dimeric ferrocene derivative (1,2-diferrocenyl-1,2) dimethyl-ethylene) are intensively mixed together by means of a speed mixer. To 10 g Diethylengklykol be given and mixed thoroughly this also means a speed mixer, a ^¬. A 50 μm thick layer is produced by means of the doctor blade technique on an ITO-coated film. This layer is transparent in transmitted light. If this layer is located between two ITO electrodes, a blue color is produced at the cathode when a voltage is applied, and a translucent color impression when illuminated.

2 Preparation of an opaque matrix with polyvinylpyrrolidone

Ig polyvinylpyrrolidone with 0.1 g of a polymeric Bipy- ridiniumsalzes (poly (dodecyl-4, 4'-bipyridinium) -dibromid) and 0.07g of a dimeric ferrocene derivative (1, 2-diferrocenyl-1, 2-dimethyl-ethylene) by means of a Speed mixers are mixed together intensely. 7g of diethylene glycol are added and these are also intensively mixed in using a speed mixer. A 50 μm thick layer is produced by means of the doctor blade technique on an ITO-coated film. This layer is transparent in transmitted light. If this layer is located between two ITO electrodes, a blue color is produced at the cathode when a voltage is applied, and a translucent color impression when illuminated.

3 Preparation of an opaque matrix with pyrromellitic anhydride

2 g of pyrromellitic anhydride are dissolved in 4 g of diethylene glycol in the heat. After cooling to room temperature, an opaque solution is obtained. 0.3 g of a poly- mers Bipyridiniumsalzes (poly (dodecyl-4, 4'-bipyridinium) - dibromide) and 0.115g of a dimeric ferrocene derivative (1,2-diferrocenyl-1, 2-dimethyl-ethylene) mixed thoroughly by means of a speed mixer. This formulation is applied by means of the rakel technique on an ITO-coated film as a layer of thickness 50 microns. This layer is transparent in transmitted light. If this layer is located between two ITO electrodes, a blue color is produced on the cathode when a voltage is applied, and a translucent color impression when illuminated.

Gradations in the light transmittance of a film produced from the Formu ^{¬-regulation} can be achieved by the layer thickness of the film and / or by the size of the dispersed particles.

The invention relates to an electrochromic formulation which is transparent in the visible spectral range. The transparency of the formulation is due to light scattering caused by particles in the formulation. The transparency can be adjusted via the particle size and the layer thickness.

Claims

claims

1. Electrochromic formulation, the following materials umfas ^¬ send: at least one chromophore and at least one relating thereto ring redox partner in a matrix and inorganic and / or organic particles, the dis- persed in the formulation are present and generate light scattering as in the matrix ,

2. Formulation according to claim 1, wherein the inorganic particles comprise one or more elements from the group of the following inorganic compounds: talc, carbonates, sulfates and phosphates of alkali and alkaline earth elements, in each case also the hydrogenderivate thereof, oxides and / or hydroxides of the metals of third and fourth main group.

3. Formulation according to one of claims 1 or 2, wherein the organic particles comprise one or more elements from the group of the following organic compounds: polyvinylpyrrolidone, polyvinylcarbazole and / or polyethylene glycol.

4. Formulation according to claim 3, wherein the organic particles are present dissolved in a solvent or solvent mixture.

A formulation according to claim 3 or 4 wherein the solvent comprises diethylene glycol.

6. Formulation according to claim 3, wherein the polyvinylpyrrolidone present in a molecular weight of about 1,300,000, the Polyvinylcarbazzol in a molecular weight of about 1,300,000 and / or the poly ^¬ ethylene glycol present in a molecular weight greater than 600,000.

A formulation according to any one of the preceding claims, wherein the chromophore and the redox partner comprise at least one compound having a polymeric 4,4'-bipyridinium structure.

A formulation according to claim 7, wherein the chromophore and the redox partner comprise at least one poly (dodecyl-4,4'-bipyridinium) dibromide.

9. Formulation according to one of the preceding claims, wherein the materials are used anhydrous.

10. A formulation according to any one of claims 1 to 3, wherein the materials are also used free of water of crystallization.

11. A process for producing a transparent electrochromic organic component by centrally arranging a formulation according to any one of the preceding claims between two transparent electrode layers.

12. Use of transparent electrochromic components in backlit status displays, windows and / or mirrors.